Exploring Time Capsule: how it fits into Apple's AirPort family

Time Capsule, announced at this years' Macworld Expo, serves as a simple rebranding of the AirPort Extreme with an integrated hard drive and power supply. Apple sells the new Time Capsule next to last years AirPort Express and the compact AirPort Express. This segment, the first of six exploring Time Capsule in depth, highlights the differences between the members of Apple's AirPort family.

Time Capsule vs Airport Extreme

Over the last several weeks, Time Capsule held a temporary advantage over last years' AirPort Extreme in its being able to work with Mac OS X 10.5 Leopard's Time Machine feature to deliver wireless automated backups. However, Apple's recent firmware upgrade has brought the existing AirPort Extreme units up to speed with Time Machine as well. So what's the difference, and is there still any need to upgrade?

This series of segments exploring Time Capsule, to be published over the course of one week, will highlight the differences in speed between the different models, in different usage patterns, and using different interfaces, all supported by real world testing in comparison with the theoretical maximum data transfers advertised. It will also answer the question: is Time Machine practical for use over wireless networking?

Previous articles related to Time Capsule and its AirPort Extreme cousin:

The recent AirPort software update included a new 5.3.1 revision to AirPort Utility, as well as firmware updates for both the 2008 Time Capsule and 2007 AirPort Extreme, both of which are now identified as using firmware version 7.3.1. Once updated to the latest firmware, shared USB disks attached to the AirPort Extreme show up in Time Machine next to the Time Capsule drive (below). Previously, AirPort Extreme shared drives only functioned as network file shares in the Finder, as described in Teardown: a look inside Apple's Time Capsule backup appliance.

Earlier "UFO" shaped models of the AirPort Extreme do not support the faster 802.11n wireless networking standard nor USB disk sharing. The compact AirPort Express model also does not support USB disk sharing. That means in order to set up network file sharing and Time Machine backups, you'll need a square AirPort Extreme purchased over the last year or so, or a new Time Capsule. Earlier AirPort base station models can be recycled by being configured to join the same network and therefore be used to expand its wireless coverage.

Never Mind the Bottlenecks, Here's Time Capsule

As depicted in Teardown: a look inside Apple's Time Capsule backup appliance, Time Capsule uses a direct SATA connection to its internal hard drive, suggesting the potential for faster drive access compared to an externally connected USB disk, the only disk sharing option available to AirPort Extreme base stations. However, the speed advantage of SATA over USB shouldn't matter, considering that most users will be accessing their base station wirelessly over a 802.11n connection that is much slower than USB. Our test result numbers support this idea.

Non-mobile machines can substantially improve their connection speed by plugging directly into the Time Capsule or AirPort Extreme using an Ethernet cable. Both units supply three LAN Ethernet ports, and these can be connected to an external Ethernet switch to supply a fast wired connection to additional number of wired machines. Both models now support Gigabit Ethernet, although early models of the AirPort Extreme sold before August 2007 only offered Fast Ethernet (10/100) ports.

That means users with Time Capsule or an "AirPort Extreme 802.11n (Gigabit Ethernet)" can access their shared drives over a wired network at Gigabit Ethernet speeds; earlier "AirPort Extreme 802.11n (Fast Ethernet)" models sold prior to August 2007 can only manage 100 Megabit Ethernet, which is theoretically slower than 802.11n wireless networking. In practice however, even Fast Ethernet is usually faster in practice than the fastest wireless.

That segues into Friday's segment, which will explore the difference between theoretical data throughput numbers and the practical speeds users will experience in the real world. Our testing will look at the speeds promised by Time Capsule's SATA, USB 2.0, 10/100/1000 Ethernet, and 802.11b/g/n wireless networking interfaces. That examination will set the stage for exploring what kind of speed users will actually see from Time Capsule, how it compares to the similar AirPort Extreme, as well as a standalone computer acting as a network file server.

Am I correct in thinking that the biggest difference between the two options (1-Time Capsule, 2- Airport Extreme plus USB connected HDD) is the ability to use the AE+HDD as a Time Machine backup AND a shared network disk (eg for media storage) which is not possible with Time Capsule?

I do believe you are wrong; the TC drive will act as a network storage device, so any computer on the network will be able to see it and grab files from/place files onto it as if it were just another network drive.

The real difference, I believe, if ease of use/cost. it's cheaper to get a TC than an AE+500GB HDD. Plus more streamlined.

i'm wondering if the apple tv (or even the mac mini) could be considered to play a role in this comparison.
they are as well very small devices and could serve as a router, as they are networked by cable and wireless. they even have audio/video output possibility and a built-in harddisk, and further external disks can be connected. their cost is higher though....

The fact that dare not speak its name is that the Airport Extreme (gigabit) drops its wireless connection so often as to be unusable - several times a day in my case. 7.3.1 firmware does not cure this. All previous base stations are solid as rocks from a connection point of view.

So I junked the AEBS and bought a Time Capsule.

It does not drop its connection when backing up wirelessly. It was worth braving the essentially dumb Apple Store staff to buy it. The 500GB model actually contains a 'Server Grade' drive.

Apple have reworked the device so it works. This may be relevant to those choosing what to buy. It also may serve to remind that Apple produces rubbish every few years.

The fact that dare not speak its name is that the Airport Extreme (gigabit) drops its wireless connection so often as to be unusable - several times a day in my case. 7.3.1 firmware does not cure this. All previous base stations are solid as rocks from a connection point of view.

Your mileage may vary. My brother's one has been solid as a rock since last year. My own AEBS (the older Fast Ethernet model) is just as robust. Both are now hosting Time Machine AirPort Disks too.

i'm wondering if the apple tv (or even the mac mini) could be considered to play a role in this comparison.
they are as well very small devices and could serve as a router, as they are networked by cable and wireless. they even have audio/video output possibility and a built-in harddisk, and further external disks can be connected. their cost is higher though....

The problem with using a mini to host your wireless network is that I believe the "software base station" option (ie, using a Mac as a base station) is limited to WEP security.

However, I am curious to see what results AppleInsider has waiting for us tomorrow and if it includes using a Mac to host the remote disk instead of either Time Capsule or an Extreme. In my experience, a FW drive connected to a Mac which is then attached to an Extreme via Ethernet blows away a USB drive connected to my Extreme and any benchmarks I've seen for Time Capsule's internal drive.

However, the speed advantage of SATA over USB shouldn't matter, considering that most users will be accessing their base station wirelessly over a 802.11n connection that is much slower than USB. Our test result numbers support this idea.

I bet it will make a difference when you have multiple Macs backing up at the same time.

I'm impressed that Apple Insider continues to propagate the myth that the Airport Extreme supports TM backups. A quick look at Apple support forums shows that there are plenty of issues with Air Disk, let alone try to push TM backups to a less-than reliable target.

Backups are, by definition, critical. Best to balance out the need for solid backups with the need to prove Apple wrong about AE TM backups.

Friday's segment I'm very much looking forward to, as this will answer some questions I've had that have so far put me off buying one.

What I'm specifically interested in is the time taken and transfer speed for doing a Time Machine backup over directly connected Gigabit ethernet. My MBP can only do 802.11g, and when I recently transfered 20GB data onto my Mini over wireless, it took about 5 hours. So doing an initial full backup or (shudder) a full restore of ~100GB over an 802.11g network is not viable.

If however the transfer speed over gigabit ethernet is quite respectable, then that changes things as I'm sure an 802.11g network will be fine for incrementals. It's going to depend on what protocol it uses (I assume AFP over TCP) and how well that's tuned for gigabit networks.

The standard TCP/IP applications (for example, ftp and NFS) are not designed to run at Gigabit speeds. I've done tests in the past with a single point to point network transfer, and under normal conditions (MTU of 1500 and TCP window size of 32768 bytes) I was only able to achieve 447Mb/s. Increasing the window size to 57344 bytes boosted the test to 496Mb/s but that was the best I got.

Faster speeds are only possible if you can increase the MTU at both ends (and anything in between) to 9000 ( a.k.a Jumbo Frames ). Combining that with a window size of 128000 bytes boosted my results to 978Mb/s. Given the Deskstar 7K1000's Media Transfer Rate of 1070Mb/s (max) it aught to be possible to get close to that. Assuming the Time Capsule can be configured to tweak its MTU above 1500.